The comparative in vitro activities of two new oxazolidinone antimicrobial agents, U-100592 and U-100766, against 180 isolates of enterococci representing several resistance profiles were examined by using an agar dilution technique. The two oxazolidinones inhibited all isolates, including strains resistant to vancomycin, ampicillin, and minocycline, at concentrations between 1 and 4 micrograms/ml.